A series of related studies are proposed to examine the behavioral pharmacology of a new partial agonist-antagonist, Buprenorphine, in a primate model. Buprenorphine has been suggested as a potential alternative to methadone for the treatment of heroin addiction, and clinical studies to evaluate its effects on heroin self-administration are currently underway in this laboratory. A primate drug self-administration model, and established operant behavioral procedures will be used to examine several issues which are relevant to the clinical deployment of Buprenorphine, but are difficult or impossible to study in man. It is proposed to: (1) Compare the effectiveness of maintenance on buprenorphine with maintenance on methadone in attenuating opiate self-administration in opiate experienced monkeys, using each monkey as its own control across conditions; (2) Study the abuse liability or reinforcing efficacy of buprenorphine (over a wide range of doses) in drug naive and opiate experienced monkeys; (3) To determine if buprenorphine will be administered concurrently with morphine, when both are available in a paradigm designed to simulate polydrug availability in man; (4) To study the dose range over which buprenorphine is maximally reinforcing in a discrete trial choice procedure. Preference for various doses of buprenorphine will be compared and relative preference for buprenorphine and morphine (at equivalent doses) will be examined. These studies should clarify the behavioral effects of buprenorphine in the primate model and suggest future directions for basic and clinical research. If concordant data are obtained in parallel primate and ongoing clinical studies, this will further validate the usefulness of this primate model for behavioral evaluation of new pharmacotherapies.